Synthesis and Hydrogenation of Bis(imino)pyridine Iron Imides

Bart, Suzanne C.; Lobkovsky, Emil; Bill, Eckhard; Chirik, Paul J.

doi:10.1021/ja057165y

Cited by 197 publications

(199 citation statements)

References 31 publications

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“…Furthermore, isolated nitrenes of late transition metals such as Fe, 7,8 Co, 8 and Ni 6,29 are known to transfer NR to CO to yield isocyanates. Given their importance and experimental scarcity, we undertook a proactive investigation of the bonding in copper nitrene complexes.…”

Section: Resultsmentioning

confidence: 99%

“…For example, Mindiola and Hillhouse have reacted a bis-(phosphine)nickel nitrene with CO to form ArNCO. 6 Bart et al 7 and Peters et al 8 have reported nitrene group transfer from structurally characterized late-transition-metal nitrene complexes (iron and cobalt, respectively) to CO to yield ArNCO. There is considerable interest in phosgene-free processes for the production of isocyanates from nitroaromatics (nitrenes are proposed as intermediates) using latetransition-metal catalysts.…”

Section: Introductionmentioning

confidence: 99%

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Bonding and Structure of Copper Nitrenes

2008

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Copper nitrenes are of interest as intermediates in the catalytic aziridination of olefins and the amination of C-H bonds. However, despite advances in the isolation and study of late-transition-metal multiply bonded complexes, a bona fide structurally characterized example of a terminal copper nitrene has, to our knowledge, not been reported.In anticipation of such a report, terminal copper nitrenes are studied from a computational perspective. The nitrene complexes studied here are of the form ( -diketiminate)Cu(NPh). Density functional theory (DFT), complete active space self-consistent-field (CASSCF) electronic structure techniques, and hybrid quantum mechanical/molecular mechanical (QM/MM) methods are employed to study such species. While DFT methods indicate that a triplet (S ) 1) is the ground state, CASSCF calculations indicate that a singlet (S ) 0) is the ground state, with only a small energy gap between the singlet and triplet. Moreover, the ground-state (open-shell) singlet copper nitrene is found to be highly multiconfigurational (i.e., biradical) and to possess a bent geometry about the nitrene nitrogen, contrasting with the linear nitrene geometry of the triplet copper nitrenes. CASSCF calculations also reveal the existence of a closed-shell singlet state with some degree of multiple bonding character for the copper-nitrene bond.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bonding and Structure of Copper Nitrenes

2008

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“…In addition, several studies have involved the reduction of 5 or 6 in the presence of nitrogen as a means of generating dinitrogen-containing complexes [53,132,133,134] .…”

Section: Well-defined Iron and Cobalt Alkylsmentioning

confidence: 99%

Iron-Based and Cobalt-Based Olefin Polymerisation Catalysts

Gibson¹,

Solan²

2008

Topics in Organometallic Chemistry

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This chapter describes the brief history of iron or cobalt catalysts for olefin polymerisation and oligomerisation. Since the discovery in 1998 that 2,6-bis(imino)pyridine iron and cobalt halides, on activation with MAO, can convert ethylene to highly linear polyethylene, numerous reports have been concerned with ligand modification, mechanisms for precatalyst activation, identifying the active species and understanding the mode of propagation/chain transfer. In addition, heterogenisation of this class of catalysts, their incorporation into macrocycles/ polymers and their use in reactor blending/tandem catalysis has seen some important developments; alternative ligand architectures that can support active iron and cobalt catalysts are also discussed as are different types of olefinic monomer.

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“…It should be noted that, as with the free ligands, the bound ligand in 1 and 2 can be the site for a range of chemistries including deprotonation (see Chapter 4 and [135,144]) . In addition several studies have involved the reduction of 1 or 2 in the presence of nitrogen as a means of generating dinitrogen -containing complexes (see Chapter 4 and [53,[145][146][147][148]) . …”

Section: Well -Defi Ned Iron and Cobalt Alkylsmentioning

confidence: 99%

Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes Bearing Bis(imino)pyridine Ligands

Gibson

Solan

2010

Catalysis Without Precious Metals

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IntroductionThe capacity of 2,6 -bis(arylimino)pyridine -iron(II) and -cobalt(II) halide complexes, on activation with methylalumoxane ( MAO ), to act as exceptionally active catalysts (comparable with Group 4 metallocenes) for the conversion of ethylene to high density polyethylene ( HDPE ) was fi rst disclosed independently by Brookhart, Bennett and ourselves in 1998 ( Figure 5.1 ) [1 -7] . The signifi cance of this discovery was further highlighted by the complete absence at the time of examples of iron and cobalt complexes in olefi n polymerization applications. In comparison with early transition metal -based catalysts such as metallocenes, these late transition metal systems offer some distinct advantages which range from their relative ease of handling and manipulation, their reduced oxophilicity, to the cost -effectiveness and low toxicity of the metal centers employed. Moreover, by simple modifi cation of the 2,6 -bis(arylimino)pyridine ligand frame, exceedingly effi cient iron and cobalt oligomerization catalysts can also be generated, facilitating the formation of highly linear α -olefi ns with near ideal Schulz -Flory distributions. Since these initial fi ndings the past decade has witnessed a dramatic growth in reports associated with this class of late transition metal catalysts, and clear structure -activity relationships have emerged.This chapter is concerned with highlighting some of the more notable advances that have come to light as a result of identifying key factors that infl uence catalyst performance, particularly those related to precatalyst structure. The importance of the initiator and the role played in chain transfer is probed. Current mechanistic understanding is examined from both a spectroscopic and a computational viewpoint while efforts to prepare well -defi ned iron or cobalt alkyl catalysts are discussed. Efforts to heterogenize these homogeneous catalysts are briefl y reviewed, as is their use in multi -component catalysis.The reader is referred to a series of reviews for more general overviews of postmetallocene α -olefi n polymerization catalysts [8 -12] , while recent reviews relating to the versatility of 2,6 -bis(imino)pyridines and to iron -and cobalt -based catalysis itself have also been documented [13 -15] .

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Synthesis and Hydrogenation of Bis(imino)pyridine Iron Imides

Cited by 197 publications

References 31 publications

Bonding and Structure of Copper Nitrenes

Bonding and Structure of Copper Nitrenes

Iron-Based and Cobalt-Based Olefin Polymerisation Catalysts

Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes Bearing Bis(imino)pyridine Ligands

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